OK, I sm somewhat of an expert in satellite data so here:

Each GPS manufacturer must launch or pay to have launched their own GPS satellite(s). The GPS unit in your car can only "speak" to it's own company's satellite. The satellites in turn "speak back" to the individual GPS units. That is why they were so expensive several years ago.

The bigger companies have more units communicating with the distinct possibility of overload or crash. This has happened many times recently with Garming and TomTom since they are the most popular. If too many people are using their GPS at the same time, the satellites overload and can actually crash into another planet, star, meteor or asteroid...or worsed case back down to Earth.

Also, the beams that are transmitted as the GPS units "speak" to the satellites can cause beam deflection errors which usually occur on bridges or the entrances to tunnels.

Also, the satellites can lock their beams to the wrong GPS units and it is possible to reeive someone elses meant transmission which force people to get totally lost. For example, you live in San Francisco but you receive the satellite beam from the TomTom satellite unit of a person living in Prague. This is why I only buy offbrand GPS units

peakbasterd is a h0m0

#1, I'm guessing that was an attempt at humor, a failed one I might add.

For an "expert", you apparently know nothing about GPS units or even how they work. For starters, GPS units don't "speak", they listen and they all listen to the same satellites, not ones the manufacturer of the GPS unit launched - no GPS unit manufacturer has ever launched a satellite.

Most of the satellites are located way up in outerspace stupid.

Wow, #1 isn't even smart enough to fix his typos before re-posting his gibberish on every GPS deal listed.